Fuse



July 27, 1937. A. L. FRENCH FUSE Filed DeG. 7, 1935 Patented July 27,1937 UNTE STATE AT @ENCE FUSE linois Application December '7, 1935,Serial No. 53,319

8 Claims. (Cl. 20u-113) The present invention is primarily concernedwith an improved fuse construction and more particularly withimprovements in fuses of the type utilizing a capillary thread of liquidconductor such as mercury, which upon iiow of excessive current, willinterrupt a circuit therethrough, but which may be reset for furtheruse, simply by moving the fuse with a snap action of the wrist.

A further object of the invention resides in irnprovernents in theconstruction of fuses of the herein described type which will enablesuch fuses to be more easily and less expensively manufactured, yet willat all times operate efficiently and reliably.

It is also an important object of the invention to provide a novelcartridge unit within which the operative parts oi' the fuse areenclosed, this cartridge being adapted for assemblywith other parts bymeans of which it may be readily connected and disconnected relative tothe circuit to be protected.

Still another object of the invention is to provide a fuse of the hereindisclosed type having improved circuit interrupting characteristics,whereby an arc extinguishing medium will be exuded from the walls of thecapillary tube under the action of the arc.

in accordance with the general features of the invention. it is proposedto provide a cartridge assembly composed of a tube of insulatingmaterial having a longitudinally extending bore of capillary caliber.This tube is reinforced at its end portions by cap members formingelectrical contacts. One of these cap members is extended to form anexpansion chamber and also provide radiating surface for the dissipationor" heat gen-- erated during the interruption oi current in the device.Abutting the tube and disposed within this chamber is a metal diskhaving a central bore arranged to register with the bore of the tube.This disk is secured in position by virtue of a press nt contact at itsperiphery with the interior wall of the expansion chamber. The tube andbore of the metal disk are arranged to be lled with a liquid conductorsuch as mercury which is adapted to vaporize when a predeterminedcurrent iiows through the thread of liquid Within the tube. Thisvaporization causes the mercury to be forced out in vapor form into theexpansion chamber where its Contact with the interior wall thereof willcause it to condense. In this connection, the efiiciency of thecartridge is also increased by virtue of constructing the tube of amaterial which under the action of the electrical arc when the circuitis broken has the characteristic of exuding a medium which operates toextinguish the arc.

An additional feature oi the invention resides in the manner of adaptingthe cartridge for connection and disconnection into a circuit to beprotected. in the novel construction disclosed on the drawings, a screwierrule having inwardly projecing iiexible tongues is provided. Thesetongues are spaced apart at their free ends so as to permit sliding theferrule axially over the cartridge with the tongues in engagement Withthe elongated cap forming the expansion charnber. These tongues alsofunction to maintain the ierruie in symmetrically spaced positionrelative to the cartridge and enable a body of non-conducting moldablematerial to be compressed around the cartridge and within the ferrule soas to form a rigid fuse plug having the outer surface of the ferrule andthe other contacts exposed.

Other objects and features of the invention will more fully appear fromthe following detailed description, taken in connection with theaccompanying drawing, which illustrates several embodiments thereof, andin which:

Figure l is a view in elevation of a fuse plug embodying the features ofthe present invention;

Figure 2 is'a similar view showing a modified body construction;

Figure 3 is an enlarged sectional view through the fuse plug, thecartridge being shown in elevation, taken substantially on line III-IIIof Figure 1;

Figure 4 is a transverse section through the fuse plug to show thecooperative engagement ben tween the tongues of the ierrule and thecartridge, taken substantially on line IV-IV of Figure 3; and

Figure 5 is an enlarged vertical sectional View taken through thecartridge assembly of the plug showing the details of its construction.

As shown on the drawing:

Figures l and 2 of the drawing disclose a preferred and modiiied form ofa ruse plug embodying the present invention. The internal constructionof the preferred and modiiied forms is identical, the only differencebeing in the external construction oi the body of the plug. In Figure 1,the portion of the body which is arranged to be grasped when insertingthe plug in a proper adapter, is circular in form, whereas in theembodiment shown in Figure 2, this portion of the plug is made polygonalso that greater pressure maybe applied while screwing the plug into andout of a receptacle. Moreover if necessary, this form of body enables awrench or other tool to Cil be applied to the body whereby still greaterforce may be utilized to remove the plug from its adapter.

Internally, the plug comprises a cartridge, generally indicated at IIJwhich is assembled to form a unitary structure and embody the operativeparts for interrupting the flow of current in a circuit to be protected,when this current reaches a predetermined high value.

The cartridge comprises a tub-e II having a longitudinallly extendingbore I2 of capillary caliber. This bore extends from one end of the tubeto the other and is arranged to be filled with a liquid conductor suchas mercury, as indicated at I3.

The tube is preferably constructed of a material which will under theinfluence of an electrical arc cXude an arc extinguishing medium. Forthis purpose, it has been found that a tube constructed of fibrousmaterial will have this property.

Intermediate the ends of the tube, the tube is provided with acircumferentially extending groove I4 which is utilized in securing thecontact members Iii and IG to the tube.

The contact member iii is in the form of a cap which surrounds one endof the tube and acts as a closure member which. is in contact with themercury in the bore of the tube. The end of the tube associated with thecap lli is provided with an end contracted portion Il which donnes anabutment shoulder Iii, this shoulder cooperating with one of the wallsof groove ld to form a cicumferentially extending bead I9 which isinwardly disposed from the end of the tube.

The cap I5 closely and tightly surrounds this end of the tube and hasits marginal rim portien 2i] deiiected into the groove i4 in abuttingengagement with one wall of the groove. This cap forms one of thecontacts of the fuse and also acts to strengthen this end of the tube.

The cap I6 is in the form of an elongated cup, and the open end of thiscup extends over the other end of the tube and is secured in like manner, that is, the rim margin of the cup inwardly deflected as shown atZI to abut the other wall of the groove I4 and retain the cup againstremoval from the tube.

The cap I6 extends outwardly of the associated end of the tube anddefines an expansion chamber 22. Within this chamber is a metallic disk23 having its periphery in press fit engagement with the interior wallof the expansion chamber. This disk abut-s the end of thc tube disposedin the chamber and is provided with a central here which is inregistration with the capillary bore I2 of the tube.

The ends of the disk 23 and tube II, which face the expansion chamber,are conically recessed as shown at 25 and 2t respectively.

With the construction just described, when an excessive current ilowsbetween the contacts at the ends of the tube, the liquid conductorwitnin the capillary bore will become vaporized and set up a pressurewhich forces the mercury or other liquid conductor outwardly into theeX- pansion chamber 22, thereby breaking the circuit between thecontacts. The vaporized mercury, of course, due to interrupting theelectric are becomes heated and its engagement with the wall of theexpansion chamber causes the mercury to condense. Since a largeradiating surface is provided in the cap It, thc heat from the mer* curywill be readily dissipated into the surround ing medium. In order toreset the fuse so that it may again carry current, the fuse containingthe cartridge is moved with a snap action of the wrist, which causes themercury to rie-establish a thread between the contacts.

The recessed portion 25 facilitates the movement of mercury from theexpansion chamber into the tube, and also during the time when themercury is forced into the expansion chamber from the tube, the recessedportion tends to act as a nozzle and enable the mercury vapor to bethrown into a greater area of contact with the wall of the expansionchamber, whereby the inercury is cooled more rapidly.

The recessed portion 2@ at the upper end of the tube tends to create aback pressure which enables mounting of the cartridge in horizontal orother position without causing the mercury to run from the capillarytube into the expan sion chamber, which would render the fuseinoperative.

The unitary cartridge assembly is susceptible of being mounted invarious types of arrangements which will permit the fuse to bc connectedand disconnectedin a circuit to be protected. For purposes ofillustration, I have chosen to show this cartridge mounted in a fuse ofthe plug type. This fuse contains screw ferrule 2l oi the usual type. Inthe construction of the fuse of this in vention, the ferrule 2l isprovided at its upper edge with a plurality, in this case four, inwardlyextending arms 2S which are flexible and formed at their inner ends toengage the outermost sur face of the cap IIS.

In the manufacture of this fuse, the ferrule is inserted over thecartridge and the arms ES resiliently engage the outer surface of thecap IIS and also serve to initially maintain the fer rule in properspaced relation during the molding of the fuse body 2S which willoperate to fixedly secure the ferrule and cartridge in assembledrelation.

The fuse body 29 is of a moldable insulating material such as rubber orporcelain. When the body has been molded, the parts are rigidly held inassembled position and the exterior of the ferrule as well as thelowermost end of the cap l5 are exposed to permit electrical connectionswith the usual screw type sockets.

From the foregoing description., it will be apparent that this inventionprovides an improved fuse construction embodying a novel cartridge whichmay be incorporated with adapter parts by means of which it may beeasily connected and disconnected relative to a circuit to be protected;an improved fuse of the type utilizing a capillary tube containing aliquid conductor which is vaporized upon the flow of excessive currentto open the circuit therethrough; and which utilizes a ferrule of suchconstruction that it is initially held in proper position relative tothe cartridge during the molding of the body portion of the fuse plug,and in which the body thereafter rigidly holds the ferrule and cartridgein assembled position. Extinguishment of the arc is augmented byproviding a tube of such material that un der the action of the are, anarc extinguishing medium is exuded. Moreover, the invention provides afuse of the type which may be reset for using again simply by moving thefuse with a snap action of the wrist.

Now, it is of course to be understood that although I have described indetail several embodiments of the invention, the invention is not to bethus limited, but only insofar as dened by the scope and spirit of theappended claims.

I claim as my invention:

1. A current interrupter comprising a capillary tube oi insulatingmaterial having an axially extending bore, a liquid conductor normallyfilling said bore, and a pair of terminals electrically connected. bythe liquid conductor inl said bore, said bore being oi such caliber thatthe liquid conductor will vaporize at a predetermined current load, andsaid terminals forming reinforcing casings around said tubesubstantially throughout its length.

2. A fuse of the character described comprising a tubular cartridge or"insulating material, metallic contacts insulated relative to each otherand respectively disposed at the ends of said cartridge, a metallicferrule surrounding said cartridge and outwardly spaced relativethereto, inwardly projecting tongues carried by said ferrule forengaging one of said contacts, a body of insulating material securingsaid cartridge and errule in assembled relation, and means within saidcartridge normally connecting said contacts and operative upon the flowof excessive current to dis* connect said contacts relative to eachother.

3. In a fuse construction, a cylindrical cartridge containing circuitinterrupting means, electrically insulated contact members on saidcartridge, a metal ierrule assembled to surround said cartridge,inwardly extending tongues on said ferrule resiliently engaging one ofsaid contacts and initially spacing said ferrule symmetrically relativeto said cartridge, and a body of non-conducting moldable materialrigidly securing the ferrule and cartridge in assembled relation withthe outer surface of the ierrule and the other Contact exposed.

fi. A fuse including a unitary cartridge assembly comprising a tubularmember of insulating material having a capillary bore and acircumierential groove disposed in its outersurface between its ends, ametallic cap tightly itting over one end of the tube and having its edgeinwardly deflected to engage one wall of said groove, an elongatedmetallic cup having its rim margin surrounding the other end of saidtube and its edge inwardly deflected to engage the other wall of saidgroove, said cup extending beyond the associated end oi the tube tokform a chamber, a metal disc in the chamber having a press fitengagement with the inner wall of; said cup and abutting the adjacentend of the tube, a passageway in said disc interconnecting said bore andchamber, and a liquid conductor in said bore completing an electricalcircuit between said cap and cup.

5. A fuse cartridge comprising a tubular member of insulating materialhaving a longitudinal bore of capillary caliber and circumferentialgroove on its outer surface, a liquid conductor normally lling saidbore, metal cap members respectively extending over the ends of saidtube and in electrical circuit with said liquid, one of said cap membersbeing extended outwardly of its associated tube end to denne anexpansion chamber, and inwardly deflected. portions of said cap membersdisposed in said groove, whereby said cap members are retained againstremoval from said tube.

6. A fuse comprising a tubular member of insulating material having acircumferentially extending groove on its outer surface, metal capmembers respectively extending over the ends oi said tube and havingtheir confronting ends deflected into said groove, said deflected endsbeing spaced apart, a non-conducting moldable material disposed in saidgroove between the deected ends oi said caps, and means in said tubenormally connecting said caps and operative upon the i'low oi excessivecurrent to disconnect said caps relative to each other.

'7. A fuse comprising a tubular member of insulating material having acircumferentially extending groove on its outer surface, metal capmembers respectively extending over the ends of said tube and havingtheir confronting ends deiiected into said groove, said deflected endsbeing spaced apart, a non-conducting moldable material surrounding thedeflected end portions of said caps and iilling the space in said groovebetween said deilected ends, and means within said tube normallyconnecting said caps and operative upon the flow or" a predeterminedcurrent to disconnect said caps relative to each other.

8. A fuse oi the character described comprising a tubular cartridge oiinsulating material, metallic contacts insulated relative to each otherand respectively disposed at the ends of said cartridge, a metallicierrule surrounding said cartridge and outwardly spaced relativethereto, means electrically connecting said ierrule and one ci saidcontacts, said means serving to initially space said errule relative tosaid cartridge, and a body ci moldable insulating material rigidlysecuring the ferrule, cartridge and means in assembled relation with theouter surface of the errule and the other contact exposed.

ALVIN L. FRENCH.

